Threshold Filtering

Threshold filters, following the guidance of Florida Department of Environmental Protection’s (FDEP) Division of Environmental Assessment and Restoration (DEAR) are used to exclude specific results values from the SEACAR Analysis. Based on the threshold filters, Quality Assurance / Quality Control (QAQC) Flags are inserted into the SEACAR_QAQCFlagCode and SEACAR_QAQC_Description columns of the export data. The Include column indicates whether the QAQC Flag will also indicate that data are excluded from analysis. No data are excluded from the data export, but the analysis scripts can use the Include column to exclude data (1 to include, 0 to exclude).

Continuous Water Quality threshold values
Parameter Name Units Low Threshold High Threshold Sensor Type
Dissolved Oxygen mg/L 0 50 YSI EXOs
Dissolved Oxygen mg/L 0 50 Analysis Only - 2022-04-04
Dissolved Oxygen mg/L 0 50 6600 Series
Salinity ppt 0 70 6600 Series
Salinity ppt 0 70 YSI EXOs
Salinity ppt 0 70 Analysis Only - 2022-04-04
Water Temperature Degrees C -5 45 YSI EXOs
Water Temperature Degrees C -5 45 Analysis Only - 2022-04-04
Water Temperature Degrees C -5 45 6600 Series
pH pH 2 14 Analysis Only - 2022-04-04
pH pH 2 14 6600 Series
pH pH 2 14 YSI EXOs
Dissolved Oxygen Saturation % 0 500 YSI EXOs
Dissolved Oxygen Saturation % 0 500 6600 Series
Dissolved Oxygen Saturation % 0 500 Analysis Only - 2022-04-04
Specific Conductivity mS/cm 0 100 6600 Series
Specific Conductivity mS/cm 0 200 YSI EXOs
Turbidity NTU 0 4000 YSI EXOs
Turbidity NTU 0 1000 6600 Series
Turbidity NTU 0 4000 Analysis Only - 2022-04-04
Discrete Water Quality threshold values
Parameter Name Units Low Threshold High Threshold
Dissolved Oxygen mg/L 0.000001 22
Salinity ppt 0 70
Water Temperature Degrees C 3 40
pH 2 13
Dissolved Oxygen Saturation % 0.000001 310
Specific Conductivity mS/cm 0.005000001 100
Turbidity NTU 0 -
Total Suspended Solids (TSS) mg/L 0 -
Chlorophyll a uncorrected for pheophytin ug/L 0 -
Chlorophyll a corrected for pheophytin ug/L 0 -
Secchi Depth m 0.000001 50
Light Extinction Coefficient m^1 0 -
Colored dissolved organic matter, CDOM PCU 0 -
Fluorescent dissolved organic matter, FDOM QSE 0 -
Total Nitrogen mg/L 0 -
Total Kjeldahl Nitrogen TKN mg/L 0 -
NO2+3 Filtered mg/L 0 -
NH4 Filtered mg/L 0 -
Total Phosphorus mg/L 0 -
PO4 Filtered mg/L 0 -
Ammonia- Un-ionized (NH3) mg/L 0 -
Nitrate (N) mg/L 0 -
Nitrite (N) mg/L 0 -
Nitrogen, organic mg/L 0 -
Quality Assurance Flags inserted based on threshold checks listed in Table 1 & 2
SEACAR QAQC Description Include SEACAR QAQCFlagCode
Exceeds Maximum threshold. Not verified in raw data No 2Q
Exceeds Maximum threshold. Verified in raw data No 3Q
Below Minimum threshold. Not verified in raw data No 4Q
Below Minimum threshold. Verified in raw data No 5Q
Within threshold tolerance Yes 6Q
No defined thresholds for this parameter Yes 7Q

Value Qualifiers

Value qualifier codes included within the data are used to exclude certain results from the analysis. The data are retained in the data export files, but the analysis uses the Include column to filter the results.

STORET and WIN value qualifier codes

Value qualifier codes from STORET and WIN data are examined with the database and used to populate the Include column in data exports.

Value Qualifier codes excluded from analysis
Qualifier Source Value Qualifier Include MDL Description
STORET-WIN H No 0 Value based on field kit determination; results may not be accurate
STORET-WIN J No 0 Estimated value
STORET-WIN V No 0 Analyte was detected at or above method detection limit
STORET-WIN Y No 0

Discrete Water Quality Value Qualifiers

The following value qualifiers are highlighted in the Discrete Water Quality section of this report. An exception is made for Program 476 - Charlotte Harbor Estuaries Volunteer Water Quality Monitoring Network and data flagged with Value Qualifier H are included for this program only.

H - Value based on field kit determiniation; results may not be accurate. This code shall be used if a field screening test (e.g., field gas chromatograph data, immunoassay, or vendor-supplied field kit) was used to generate the value and the field kit or method has not been recognized by the Department as equivalent to laboratory methods.

I - The reported value is greater than or equal to the laboratory method detection limit but less than the laboratory practical quantitation limit.

Q - Sample held beyond the accepted holding time. This code shall be used if the value is derived from a sample that was prepared or analyzed after the approved holding time restrictions for sample preparation or analysis.

S - Secchi disk visible to bottom of waterbody. The value reported is the depth of the waterbody at the location of the Secchi disk measurement.

U - Indicates that the compound was analyzed for but not detected. This symbol shall be used to indicate that the specified component was not detected. The value associated with the qualifier shall be the laboratory method detection limit. Unless requested by the client, less than the method detection limit values shall not be reported

Systemwide Monitoring Program (SWMP) value qualifier codes

Value qualifier codes from the SWMP continuous program are examined with the database and used to populate the Include column in data exports. SWMP Qualifier Codes are indicated by QualifierSource=SWMP.

SWMP Value Qualifier codes
Qualifier Source Value Qualifier Include Description
SWMP -1 Yes Optional parameter not collected
SWMP -2 No Missing data
SWMP -3 No Data rejected due to QA/QC
SWMP -4 No Outside low sensor range
SWMP -5 No Outside high sensor range
SWMP 0 Yes Passed initial QA/QC checks
SWMP 1 No Suspect data
SWMP 2 Yes Reserved for future use
SWMP 3 Yes
SWMP 4 Yes Historical: Pre-auto QA/QC
SWMP 5 Yes Corrected data

Water Column

The water column habitat extends from the surface of all water bodies to the bottom sediments and encompasses the different features found in the water at different depths (National Oceanographic Center, 2016). The water column habitat must be viewed in relation to its interconnectedness with other habitats. A healthy water column is an integral component in ensuring a healthy marine and coastal ecosystem. Having a flourishing marine and coastal ecosystem in Florida is necessary to support a strong economy. The health of the water column is dependent upon factors as diverse as land use (e.g., agriculture, mining, forestry practices); human population growth; emissions, (e.g., power plants, automobiles, wastewater); climate (e.g., rainfall, temperature, winds and currents); and decadal trends (e.g., El Niño/La Niña, Atlantic Multidecadal Oscillation, climate change).

The water column is composed of various physical, chemical and biological features, and only a small number of them are adequately monitored. Features of the water column that are monitored are used as indicators of the water column health and help assess the status of other habitats. These indicators include nutrient concentrations (nitrogen and phosphorus); water quality (dissolved oxygen, temperature, salinity and pH); water clarity (Secchi depth, turbidity, chlorophyll-a and colored dissolved organic matter); and nekton (fish, macroinvertebrates and megafauna).

Seasonal Kendall-Tau Analysis

Indicators must have a minimum of five to ten years, depending on the habitat, of data within the geographic range of the analysis to be included in the analysis. Ten years of data are required for discrete parameters, and five years of data are required for continuous parameters. If there are insufficient years of data, the number of years of data available will be noted and labeled as “insufficient data to conduct analysis”. Further, for the preferred Seasonal Kendall-Tau test, there must be data from at least two months in common across at least two consecutive years within the RCP managed area being analyzed. Values that pass both of these tests will be included in the analysis and be labeled as Use_In_Analysis = TRUE. Any that fail either test will be excluded from the analyses and labeled as Use_In_Analysis = FALSE.

Water Quality - Discrete

The following files were used in the discrete analysis:

  • Combined_WQ_WC_NUT_Chlorophyll_a_corrected_for_pheophytin-2024-Mar-27.txt

  • Combined_WQ_WC_NUT_Chlorophyll_a_uncorrected_for_pheophytin-2024-Mar-27.txt

  • Combined_WQ_WC_NUT_Colored_dissolved_organic_matter_CDOM-2024-Mar-27.txt

  • Combined_WQ_WC_NUT_Dissolved_Oxygen-2024-Mar-27.txt

  • Combined_WQ_WC_NUT_Dissolved_Oxygen_Saturation-2024-Mar-27.txt

  • Combined_WQ_WC_NUT_pH-2024-Mar-27.txt

  • Combined_WQ_WC_NUT_Salinity-2024-Mar-27.txt

  • Combined_WQ_WC_NUT_Secchi_Depth-2024-Mar-27.txt

  • Combined_WQ_WC_NUT_Total_Nitrogen-2024-Mar-27.txt

  • Combined_WQ_WC_NUT_Total_Phosphorus-2024-Mar-27.txt

  • Combined_WQ_WC_NUT_Total_Suspended_Solids_TSS-2024-Mar-27.txt

  • Combined_WQ_WC_NUT_Turbidity-2024-Mar-27.txt

  • Combined_WQ_WC_NUT_Water_Temperature-2024-Mar-27.txt

Chlorophyll a, Uncorrected for Pheophytin - Discrete Water Quality

Seasonal Kendall-Tau Trend Analysis
Discrete Water Quality
Map showing location of Discrete sampling sites for Chlorophyll a, Uncorrected for Pheophytin
Discrete Water Quality
The bubble size on the above plots reflects the amount of data available at each sampling site

Programs contributing data for Chlorophyll a, Uncorrected for Pheophytin
ProgramID N_Data YearMin YearMax
514 902 2001 2023
103 131 2020 2021
5002 19 2019 2022

Program names:

514 - Florida LAKEWATCH Program
103 - EPA STOrage and RETrieval Data Warehouse (STORET)
5002 - Florida STORET / WIN

Value Qualifiers

  • N_Total is total amount of data for a given year
  • N_ is the total amount of values flagged with the respective value qualifier in a given year
  • perc_ is the percent of data flagged with the respective value qualifier as a proportion of N_Total
Value Qualifiers for Chlorophyll a, Uncorrected for Pheophytin
Year N_Total N_I perc_I N_Q perc_Q N_U perc_U
2019 75 1 1.3
2020 47 1 2.1
2021 206 1 0.5 5 2.4
2022 88 14 15.9 1 1.1
2023 28 7 25.0 3 10.7

Note: 1I - Reported value is greater than or equal to lab method detection limit, but less than quantitation limit 2Q - Sample held beyond the accepted holding time 3U - Compound was analyzed for but not detected

Programs containing Value Qualified data:

514 - Florida LAKEWATCH Program
5002 - Florida STORET / WIN

Colored Dissolved Organic Matter - Discrete Water Quality

Colored Dissolved Organic Matter (CDOM) occurs naturally in every water body. It is made up of mainly plant material, algae and bacteria. The composition is determined by its source; plants, soil, algae, and wastewater are common sources.

Seasonal Kendall-Tau Trend Analysis
Discrete Water Quality
Map showing location of Discrete sampling sites for Colored Dissolved Organic Matter
Discrete Water Quality
The bubble size on the above plots reflects the amount of data available at each sampling site

Programs contributing data for Colored Dissolved Organic Matter
ProgramID N_Data YearMin YearMax
514 319 2001 2023

Program names:

514 - Florida LAKEWATCH Program

Value Qualifiers

  • N_Total is total amount of data for a given year
  • N_ is the total amount of values flagged with the respective value qualifier in a given year
  • perc_ is the percent of data flagged with the respective value qualifier as a proportion of N_Total
Value Qualifiers for Colored Dissolved Organic Matter
Year N_Total N_Q perc_Q
2020 21 21 100
2021 7 7 100
2022 21 21 100
2023 14 14 100

Note: 1Q - Sample held beyond the accepted holding time

Programs containing Value Qualified data:

514 - Florida LAKEWATCH Program

Dissolved Oxygen - Discrete Water Quality

Dissolved Oxygen (DO) is a key indicator of water quality. Oxygen enters surface waters by air-sea gas exchange, by wind action, or as a byproduct of aquatic plant photosynthesis. The actual quantity of DO in aquatic environments is dependent on the above processes as well as water temperature and salinity.

Seasonal Kendall-Tau Trend Analysis
Discrete Water Quality
Map showing location of Discrete sampling sites for Dissolved Oxygen
Discrete Water Quality
The bubble size on the above plots reflects the amount of data available at each sampling site

Programs contributing data for Dissolved Oxygen
ProgramID N_Data YearMin YearMax
5002 5829 1998 2022
69 999 1998 2017
469 532 2016 2023
557 148 2005 2021
95 86 2004 2018
103 15 2021 2021

Program names:

5002 - Florida STORET / WIN
69 - Fisheries-Independent Monitoring (FIM) Program
469 - Central Panhandle Aquatic Preserve WQ Monitoring
557 - Central Panhandle Aquatic Preserves Seagrass Monitoring
95 - Harmful Algal Bloom Marine Observation Network
103 - EPA STOrage and RETrieval Data Warehouse (STORET)

There are no qualifying Value Qualifiers for Dissolved Oxygen in Alligator Harbor Aquatic Preserve

pH - Discrete Water Quality

The pH of water is the measure of how acidic or basic the water body is on a scale of 0-14, with lower readings indicating acidic and higher readings indicating basic, and a pH of 7 being neutral. Florida’s natural waters fall between 6.5 and 8.5 on this scale. A water body’s pH can change due to precipitation, geology, vegetation, water pollution and air pollution.

Seasonal Kendall-Tau Trend Analysis
Discrete Water Quality
Map showing location of Discrete sampling sites for pH
Discrete Water Quality
The bubble size on the above plots reflects the amount of data available at each sampling site

Programs contributing data for pH
ProgramID N_Data YearMin YearMax
5002 2810 1998 2022
69 989 1998 2017
469 532 2016 2023
558 180 2008 2014
557 127 2005 2021
95 82 2008 2018
103 15 2021 2021

Program names:

5002 - Florida STORET / WIN
69 - Fisheries-Independent Monitoring (FIM) Program
469 - Central Panhandle Aquatic Preserve WQ Monitoring
558 - Franklin County Coastal Waters Seagrass Monitoring
557 - Central Panhandle Aquatic Preserves Seagrass Monitoring
95 - Harmful Algal Bloom Marine Observation Network
103 - EPA STOrage and RETrieval Data Warehouse (STORET)

There are no qualifying Value Qualifiers for pH in Alligator Harbor Aquatic Preserve

Salinity - Discrete Water Quality

Salinity is a measure of the amount of salt in the water. In estuarine ecosystems, salinity is influenced by precipitation, evaporation, surface-water inputs, and exchange with coastal waters.

Seasonal Kendall-Tau Trend Analysis
Discrete Water Quality
Map showing location of Discrete sampling sites for Salinity
Discrete Water Quality
The bubble size on the above plots reflects the amount of data available at each sampling site

Programs contributing data for Salinity
ProgramID N_Data YearMin YearMax
5002 6810 1998 2022
69 997 1998 2017
469 532 2016 2023
558 258 2008 2014
557 148 2005 2021
95 100 1996 2018

Program names:

5002 - Florida STORET / WIN
69 - Fisheries-Independent Monitoring (FIM) Program
469 - Central Panhandle Aquatic Preserve WQ Monitoring
558 - Franklin County Coastal Waters Seagrass Monitoring
557 - Central Panhandle Aquatic Preserves Seagrass Monitoring
95 - Harmful Algal Bloom Marine Observation Network

There are no qualifying Value Qualifiers for Salinity in Alligator Harbor Aquatic Preserve

Secchi Depth - Discrete Water Quality

Secchi depth is a measure of the transparency or clarity of the water by a device called a Secchi disk. A Secchi disk is a black and white disk that is lowered into the water on a cord. The Secchi depth is the depth at which the disk can no longer be seen. The deeper the Secchi depth, the greater the water clarity.

Seasonal Kendall-Tau Trend Analysis
Discrete Water Quality
Map showing location of Discrete sampling sites for Secchi Depth
Discrete Water Quality
The bubble size on the above plots reflects the amount of data available at each sampling site

Programs contributing data for Secchi Depth
ProgramID N_Data YearMin YearMax
69 990 1998 2017
514 910 2001 2023
558 331 2008 2017
557 79 2005 2021
5002 24 2019 2022
103 10 2021 2021

Program names:

69 - Fisheries-Independent Monitoring (FIM) Program
514 - Florida LAKEWATCH Program
558 - Franklin County Coastal Waters Seagrass Monitoring
557 - Central Panhandle Aquatic Preserves Seagrass Monitoring
5002 - Florida STORET / WIN
103 - EPA STOrage and RETrieval Data Warehouse (STORET)

Value Qualifiers

  • N_Total is total amount of data for a given year
  • N_ is the total amount of values flagged with the respective value qualifier in a given year
  • perc_ is the percent of data flagged with the respective value qualifier as a proportion of N_Total
Value Qualifiers for Secchi Depth
Year N_Total N_S perc_S
2020 102 35 34.3
2021 119 33 27.7
2022 88 20 22.7
2023 28 14 50.0

Note: 1S - Secchi disk visible to bottom of waterbody

Programs containing Value Qualified data:

514 - Florida LAKEWATCH Program
5002 - Florida STORET / WIN

Total Nitrogen - Discrete Water Quality

Nitrogen and Phosphorous are key nutrients that provide nourishment essential for the growth and maintenance of aquatic plants and animals; however, excess nutrients can cause harmful algal blooms and other water quality concerns. Nutrients enter water bodies several ways, including runoff from rain events and atmospheric deposition from natural and industrial sources.

Total Nitrogen Calculation:

The logic for calculated Total Nitrogen was provided by Kevin O’Donnell and colleagues at FDEP (with the help of Jay Silvanima, Watershed Monitoring Section). The following logic is used, in this order, based on the availability of specific nitrogen components.

  1. TN = TKN + NO3O2;
  2. TN = TKN + NO3 + NO2;
  3. TN = ORGN + NH4 + NO3O2;
  4. TN = ORGN + NH4 + NO2 + NO3;
  5. TN = TKN + NO3;
  6. TN = ORGN + NH4 + NO3;

Additional Information:

  • Rules for use of sample fraction:
    • FDEP report that if both “Total” and “Dissolved” are reported, only “Total” is used. If the total is not reported, they do use dissolved as a best available replacement.
    • An analysis of all SEACAR data shows that 90% of all possible TN calculations can be done using nitrogen components with the same sample fraction, rather than use nitrogen components with mixed total/dissolved sample fractions. In other words, TN can be calculated when TKN and NO3O2 are both total sample fraction, or when both are dissolved sample fraction. This is important, because then the calculated TN value is not based on components with mixed sample fractions.
  • Values inserted into data:
    • ParameterName = “Total Nitrogen”
    • SEACAR_QAQCFlagCode = “1Q”
    • SEACAR_QAQC_Description = “SEACAR Calculated”
      Seasonal Kendall-Tau Trend Analysis
      Discrete Water Quality
      Map showing location of Discrete sampling sites for Total Nitrogen
      Discrete Water Quality
      The bubble size on the above plots reflects the amount of data available at each sampling site
Programs contributing data for Total Nitrogen
ProgramID N_Data YearMin YearMax
514 905 2001 2023
5002 465 2001 2022

Program names:

514 - Florida LAKEWATCH Program
5002 - Florida STORET / WIN

Value Qualifiers

  • N_Total is total amount of data for a given year
  • N_ is the total amount of values flagged with the respective value qualifier in a given year
  • perc_ is the percent of data flagged with the respective value qualifier as a proportion of N_Total
Value Qualifiers for Total Nitrogen
Year N_Total N_Q perc_Q
2020 67 14 20.9
2022 81 14 17.3

Note: 1Q - Sample held beyond the accepted holding time

Programs containing Value Qualified data:

514 - Florida LAKEWATCH Program

Total Phosphorus - Discrete Water Quality

Seasonal Kendall-Tau Trend Analysis
Discrete Water Quality
Map showing location of Discrete sampling sites for Total Phosphorus
Discrete Water Quality
The bubble size on the above plots reflects the amount of data available at each sampling site

Programs contributing data for Total Phosphorus
ProgramID N_Data YearMin YearMax
514 912 2001 2023
103 61 2020 2021
5002 24 2012 2022

Program names:

514 - Florida LAKEWATCH Program
103 - EPA STOrage and RETrieval Data Warehouse (STORET)
5002 - Florida STORET / WIN

Value Qualifiers

  • N_Total is total amount of data for a given year
  • N_ is the total amount of values flagged with the respective value qualifier in a given year
  • perc_ is the percent of data flagged with the respective value qualifier as a proportion of N_Total
Value Qualifiers for Total Phosphorus
Year N_Total N_I perc_I N_Q perc_Q
2020 75 6 8.0 7 9.3
2021 122 8 6.6 7 5.7
2022 81 5 6.2 14 17.3
2023 28 16 57.1

Note: 1I - Reported value is greater than or equal to lab method detection limit, but less than quantitation limit 2Q - Sample held beyond the accepted holding time

Programs containing Value Qualified data:

514 - Florida LAKEWATCH Program
5002 - Florida STORET / WIN

Turbidity - Discrete Water Quality

Turbidity results from suspended solids in the water, including silts, clays, tannins, industrial wastes, sewage and plankton, which are all factors that contribute to how clouded or murky a water column is. Turbidity is caused by soil erosion, excess nutrients, pollutants, and physical forces such as winds, currents and bottom feeders.

Seasonal Kendall-Tau Trend Analysis
Discrete Water Quality
Map showing location of Discrete sampling sites for Turbidity
Discrete Water Quality
The bubble size on the above plots reflects the amount of data available at each sampling site

Programs contributing data for Turbidity
ProgramID N_Data YearMin YearMax
5002 3543 1998 2022
469 161 2021 2023
103 5 2021 2021

Program names:

5002 - Florida STORET / WIN
469 - Central Panhandle Aquatic Preserve WQ Monitoring
103 - EPA STOrage and RETrieval Data Warehouse (STORET)

There are no qualifying Value Qualifiers for Turbidity in Alligator Harbor Aquatic Preserve

Water Temperature - Discrete Water Quality

Temperature determines the capacity of water to hold oxygen. Cooler water can hold more dissolved oxygen because water molecules are more tightly packed, making it harder for oxygen to escape. Additionally, as water temperature increases, fish and other aquatic organisms become more active and consume oxygen at a faster rate.

Seasonal Kendall-Tau Trend Analysis
Discrete Water Quality
Map showing location of Discrete sampling sites for Water Temperature
Discrete Water Quality
The bubble size on the above plots reflects the amount of data available at each sampling site

Programs contributing data for Water Temperature
ProgramID N_Data YearMin YearMax
5002 7037 1998 2022
69 1003 1998 2017
469 532 2016 2023
558 271 2008 2017
557 148 2005 2021
95 98 1996 2018
103 15 2021 2021

Program names:

5002 - Florida STORET / WIN
69 - Fisheries-Independent Monitoring (FIM) Program
469 - Central Panhandle Aquatic Preserve WQ Monitoring
558 - Franklin County Coastal Waters Seagrass Monitoring
557 - Central Panhandle Aquatic Preserves Seagrass Monitoring
95 - Harmful Algal Bloom Marine Observation Network
103 - EPA STOrage and RETrieval Data Warehouse (STORET)

There are no qualifying Value Qualifiers for Water Temperature in Alligator Harbor Aquatic Preserve

Water Quality - Continuous

The following files were used in the continuous analysis:

  • Combined_WQ_WC_NUT_cont_Dissolved_Oxygen_NW-2024-Mar-23.txt

  • Combined_WQ_WC_NUT_cont_Dissolved_Oxygen_Saturation_NW-2024-Mar-23.txt

  • Combined_WQ_WC_NUT_cont_pH_NW-2024-Mar-23.txt

  • Combined_WQ_WC_NUT_cont_Salinity_NW-2024-Mar-23.txt

  • Combined_WQ_WC_NUT_cont_Turbidity_NW-2024-Mar-23.txt

  • Combined_WQ_WC_NUT_cont_Water_Temperature_NW-2024-Mar-23.txt

Continuous Water Quality
Map showing Continuous Water Quality Monitoring sampling locations within the boundaries of Alligator Harbor Aquatic Preserve. Sites marked as Use In Analysis are featured in this report.

Submerged Aquatic Vegetation

The data file used is: All_SAV_Parameters-2024-Mar-29.txt

Submerged aquatic vegetation (SAV) refers to plants and plant-like macroalgae species that live entirely underwater. The two primary categories of SAV inhabiting Florida estuaries are benthic macroalgae and seagrasses. They often grow together in dense beds or meadows that carpet the seafloor. Macroalgae include multicellular species of green, red and brown algae that often live attached to the substrate by a holdfast. They tend to grow quickly and can tolerate relatively high nutrient levels, making them a threat to seagrasses and other benthic habitats in areas with poor water quality. In contrast, seagrasses are grass-like, vascular, flowering plants that are attached to the seafloor by extensive root systems. Seagrasses occur throughout the coastal areas of Florida, including protected bays and lagoons as well as deeper offshore waters on the continental shelf. Seagrasses have taken advantage of the broad, shallow shelf and clear water to produce two of the most extensive seagrass beds anywhere in continental North America.

Parameters

Percent Cover measures the fraction of an area of seafloor that is covered by SAV, usually estimated by evaluating multiple small areas of seafloor. Percent cover is often estimated for total SAV, individual types of vegetation (seagrass, attached algae, drift algae) and individual species.

Frequency of Occurrence was calculated as the number of times a taxon was observed in a year divided by the number of sampling events, multiplied by 100. Analysis is conducted at the quadrat level and is inclusive of all quadrats (i.e., quadrats evaluated using Braun-Blanquet, modified Braun-Blanquet, and percent cover.”

Species

Turtle grass (Thalassia testudinum) is the largest of the Florida seagrasses, with longer, thicker blades and deeper root structures than any of the other seagrasses. It is considered a climax seagrass species.

Shoal grass (Halodule wrightii) is an early colonizer of vegetated areas and usually grows in water too shallow for other species except widgeon grass. It can often tolerate larger salinity ranges than other seagrass species. Shoal grass is characterized by thin, flat blades, that are narrower than turtle grass blades.

Manatee grass (Syringodium filiforme) is easily recognizable because its leaves are thin and cylindrical instead of the flat, ribbon-like form shared by many other seagrass species. The leaves can grow up to half a meter in length. Manatee grass is usually found in mixed seagrass beds or small, dense monospecific patches.

Widgeon grass (Ruppia maritima) grows in both fresh and salt water and is widely distributed throughout Florida’s estuaries in less saline areas, particularly in inlets along the east coast. This species resembles shoal grass in certain environments but can be identified by the pointed tips of its leaves.

Three species of Halophila spp. are found in Florida - Star grass (Halophila engelmannii), Paddle grass (Halophila decipiens), and Johnson’s seagrass (Halophila johnsonii). These are smaller, more fragile seagrasses than other Florida species and are considered ephemeral. They grow along a single long rhizome, with short blades. These species are not well-studied, although surveys are underway to define their ecological roles.

Notes

Star grass, Paddle grass, and Johnson’s seagrass will be grouped together and listed as Halophila spp. in the following managed areas. This is because several surveys did not specify to the species level:

  • Banana River Aquatic Preserve

  • Indian River-Malabar to Vero Beach Aquatic Preserve

  • Indian River-Vero Beach to Ft. Pierce Aquatic Preserve

  • Jensen Beach to Jupiter Inlet Aquatic Preserve

  • Loxahatchee River-Lake Worth Creek Aquatic Preserve

  • Mosquito Lagoon Aquatic Preserve

  • Biscayne Bay Aquatic Preserve

  • Florida Keys National Marine Sanctuary

SAV - Temporal Scope
Maps showing the temporal scope of SAV sampling sites within the boundaries of Alligator Harbor Aquatic Preserve by Program name.

Sampling locations by Program:

SAV - Sampling Map
Map showing SAV sampling sites within the boundaries of Alligator Harbor Aquatic Preserve. The point size reflects the number of samples at a given sampling site.

Central Panhandle Aquatic Preserves Seagrass Monitoring - Program 557
N_Data YearMin YearMax Collection Method Sample Locations
423 2009 2022 Braun Blanquet 14
Franklin County Coastal Waters Seagrass Monitoring - Program 558
N_Data YearMin YearMax Collection Method Sample Locations
2984 2009 2017 Percent Cover 38

SAV
Median percent cover by species in Alligator Harbor Aquatic Preserve. Linear mixed-effects models are applied to each species to produce species trends. The trendlines are then isolated and reproduced below for ease of viewing. The LME results are available in table form beneath the supplemental trendplot below.
SAV

SAV
SAV

SAV
Generalized additive models for each species in Alligator Harbor Aquatic Preserve. Species must have at least 10 years of data to be evaluated.

Drift algae, Total seagrass, Attached algae, No grass in Quadrat, and Total SAV are excluded from the analyses.